I'm old and have been in this industry a long time, and I'm genuinely surprised on those oh-so-rare occasions when what you describe doesn't happen.

Prototypes-become-products is a trope much like _The Mythical Man Month_. We all nod knowingly when it is mentioned, we all know how it will turn out, and then we (well, management dictates that we...) turn right around and do the opposite.